Magnetic recording and reproducing apparatus

Abstract

A magnetic recording and reproducing apparatus including a recording head, reproducing heads and reproducing pre-amplifiers each mounted on a rotating cylinder for allowing recording and reproducing operations at the same time, in which two signal channels are defined by first and second double azimuth heads each made up of two reproducing heads and first and second integrated circuits are arranged on the rotating cylinder in close proximity to the first and second double azimuth heads, respectively. Each of the integrated circuits includes two pre-amplifiers corresponding to two reproducing heads of the first or second double azimuth head and selectively outputs one of two amplified reproduced signals from the above pre-amplifiers which is higher in signal level, and a head discrimination signal is added to the output signal. The input part of each reproducing pre-amplifier is constructed to perform a differential operation, and one of the output signals of the first and second integrated circuits is selectively sent to a fixed side through a single transmission means in accordance with a control signal supplied from the outside. The magnetic recording and reproducing apparatus having the above construction can be made small in jitter and crosstalk, and can reduce the number of elements for transmitting signals between the rotating cylinder and the fixed side.

We claim: 
     
       1. A magnetic recording and reproducing apparatus for performing a reproducing operation simultaneously with a recording operation, comprising: a rotating cylinder;   a pair of recording heads mounted on the rotating cylinder;   first and second reproducing head groups, each formed of first and second double azimuth reproducing heads, mounted on the rotating cylinder and corresponding to first and second reproducing channels, respectively;   first circuit means mounted on the rotating cylinder in close proximity to the first reproducing head group, including reproducing pre-amplifiers for amplifying output signals of the reproducing heads of the first reproducing head group, for alternately selecting the amplified output signals and mixing the alternately selected amplified output signals with azimuth discriminating information to produce a first reproduced signal;   second circuit means mounted on the rotating cylinder in close proximity to the second reproducing head group, including reproducing pre-amplifiers for amplifying output signals of the reproducing heads of the second reproducing head group, for alternately selecting the amplified output signals and mixing the alternately selected amplified output signals with azimuth discriminating information to produce a second reproduced signal;   signal-transmission means for supplying a recording signal to the recording heads; and   channel-signal selecting/outputting means for selectively outputting one of the first and second reproduced signals in accordance with an external channel selecting signal.   
     
     
       2. A magnetic recording and reproducing apparatus according to claim 1, wherein an input part of each reproducing pre-amplifier performs a differential operation. 
     
     
       3. A magnetic recording and reproducing apparatus according to claim 1, wherein the channel-signal selecting/outputting means includes first and second rotary transformers for respectively outputting the first and second reproduced signals from the rotating cylinder. 
     
     
       4. A magnetic recording and reproducing apparatus according to claim 3, wherein each of the first and second circuit means further includes: means for comparing levels of the amplified output signals with each other;   switching means for outputting one of the amplified output signals which has a higher level in response to an output of the comparing means;   means for generating a head discriminating signal in response to the output of the comparing means; and   means for mixing the head discriminating signal with the amplified output signal outputted from the switching means.   
     
     
       5. A magnetic recording and reproducing apparatus according to claim 3, wherein the external channel selecting signal is synchronized with field periods of a video signal, and wherein the channel-signal selecting/outputting means includes: means for selecting one of the first and second reproduced signals in accordance with the external channel selecting signal;   means for generating a channel discriminating signal corresponding to the azimuth discriminating information mixed in the first and second reproduced signals in response to the first and second reproduced signals outputted by the first and second rotary transformers; and   filter means for extracting a video signal from the first and second reproduced signals outputted by the first and second rotary transformers.   
     
     
       6. A magnetic recording and reproducing apparatus according to claim 1, wherein the recording and reproducing heads and the first and second circuit means are mounted on the rotating cylinder symmetrically with respect to an axis of rotation of the rotating cylinder. 
     
     
       7. A magnetic recording and reproducing apparatus for performing a reproducing operation simultaneously with a recording operation, comprising; a rotating cylinder;   a pair of recording heads mounted on the rotating cylinder;   first and second reproducing head groups, each formed of first and second double azimuth reproducing heads, mounted on the rotating cylinder and corresponding to first and second reproducing channels, respectively;   first circuit means mounted on the rotating cylinder in close proximity to the first reproducing head group, including reproducing pre-amplifiers for amplifying output signals of the reproducing heads of the first reproducing head group, for alternately selecting the amplified output signals and mixing the alternately selected amplified output signals with azimuth discriminating information to produce a first reproduced signal, and for selectively outputting the first reproduced signal in accordance with a channel selecting signal;   second circuit means mounted on the rotating cylinder in close proximity to the second reproducing head group, including reproducing pre-amplifiers for amplifying output signals of the reproducing heads of the second reproducing head group, for alternately selecting the amplified output signals and mixing the alternately selected amplified output signals with azimuth discriminating information to produce a second reproduced signal, and for selectively outputting the second reproduced signal in accordance with the channel selecting signal;   first signal-transmission means for supplying a recording signal to the recording heads; and   second signal-transmission means made up of a brush and a rotary ring for supplying the first and second circuit means with the channel selecting signal, the channel selecting signal being an external channel selecting signal, and for successively outputting the alternately selected first and second reproduced signals such that the successively outputted alternately selected first and second reproduced signals are superposed on the channel selecting signal.   
     
     
       8. A magnetic recording and reproducing apparatus according to claim 7, wherein an input part of each reproducing pre-amplifier performs a differential operation. 
     
     
       9. A magnetic recording and reproducing apparatus according to claim 7, wherein each of the first and second circuit means includes means for comparing the levels of reproduced signals from reproducing heads for forming a reproducing head group, switching means for outputting that one of the reproduced signals which has a higher level in response to the output of the comparing means, means for generating a head discriminating signal in response to the output of the comparing means, means for mixing the head discriminating signal with the output signal of the switching means, and means for controlling the application of the output signal of the mixing means to the second signal-transmission means in accordance with the channel selecting signal sent by the second signal-transmission means. 
     
     
       10. A magnetic recording and reproducing apparatus according to claim 7, wherein the first signal-transmission means is made up of a brush and a rotary ring, and wherein the apparatus further comprises an erasing head mounted on the rotating cylinder, an erasing-signal generator and a power source each provided on a fixed side, a mixer means provided on the fixed side for mixing an erasing signal from the erasing-signal generator with a source voltage from the power source, a third signal-transmission means made up of a brush and a rotary ring for transmitting the output signal of the mixer means to the rotating cylinder, and signal separating means provided on the rotating cylinder for extracting the erasing signal and the source voltage separately from the output signal of the mixer means. 
     
     
       11. A magnetic recording and reproducing apparatus according to claim 9, wherein the head-discriminating-signal generating means includes means for generating a difference in D.C. level between the reproduced signals from reproducing heads for forming the reproducing head group, and wherein the signal application control means includes two emitter-follower circuits which include PNP transistor and NPN transistor coupled with each other and each of the emitter-follower circuits is formed of a complementary circuit (PNP-NPN, or NPN-PNP) and are alternately turned on in accordance with high and low levels of the channel selecting signal. 
     
     
       12. In a magnetic recording and reproducing apparatus for performing a reproducing operation simultaneously with a recording operation, the apparatus including a recording head, at least one reproducing head, and at least one recording pre-amplifier for the at least one reproducing head, each mounted on a rotating cylinder, the improvement wherein an output part of a recording amplifier for supplying a recording current to the recording head is constructed to perform a differential operation, and an input part of the reproducing pre-amplifier is constructed to perform a differential operation. 
     
     
       13. A magnetic recording and reproducing apparatus according to claim 12, wherein a recording signal from a fixed side is transmitted to the rotating cylinder through first rotary transformer means, a signal which is produced by the reproducing head and then amplified by the reproducing pre-amplifier, is transmitted to the fixed side through second rotary transformer means, and the first and second rotary transformer means make use of a magnetic core in common. 
     
     
       14. A magnetic recording and reproducing apparatus of the rotating head type for reproducing a video signal from a magnetic tape by two double azimuth heads, the video signal being recorded on the magnetic tape by using two recording heads having different gap azimuth angles, alternately at intervals of one field, the apparatus comprising: pre-amplifiers mounted on a rotating cylinder for amplifying reproduced signals from reproducing heads making up first and second double azimuth heads;   comparator means mounted on the rotating cylinder for comparing the levels of reproduced signals from two reproduced head making up one of the first and second double azimuth head;   switching means mounted on the rotating cylinder for outputting that one of reproduced signals from two reproducing heads making up one of the first and second double azimuth heads which is higher in signal level, in response to the output of the comparator means;   discriminating-signal generating means mounted on the rotating cylinder for generating an azimuth discriminating signal capable of indicating the gap azimuth of the reproducing head corresponding to the output signal of the switching means in response to the output of the comparator means;   mixer means mounted on the rotating cylinder for mixing the azimuth discriminating signal with the output signal of the switching means;   means for taking out the output signal of the mixer means from the rotating cylinder so that a continuous signal is formed;   a reproduced-signal processing circuit for demodulating the continuous signal to output a video signal; and   a discriminating circuit for judging the gap azimuth of the recording head corresponding to the reproduced signal, from the azimuth discriminating signal included in the continuous signal, and for sending a signal necessary for reproducing a chrominance signal correctly, to the reproduced-signal processing circuit.   
     
     
       15. A magnetic recording and reproducing apparatus for performing a recording operation simultaneously with a recording operation while substantially eliminating crosstalk between the recording operation and the reproducing operation, comprising: a rotating cylinder;   a fixed cylinder;   rotary transformer means provided between the fixed cylinder and the rotating cylinder;   a recording head mounted on the rotating cylinder and having two input terminals for receiving respective recording signals;   a reproducing head mounted on the rotating cylinder and having two output terminals for outputting respective reproduced signals;   reproducing amplifier means for amplifying the reproduced signals from the reproducing head, the reproducing amplifier means being mounted on the rotary cylinder and having a differential input including two input terminals for receiving the reproduced signals from the two output terminals of the reproducing head, and having a differential output including two output terminals for outputting the amplified reproduced signals to the fixed cylinder through the rotary transformer means; and   recording amplifier means for supplying the recording signals to the recording head, the recording amplifier means having a differential output including two output terminals for supplying the recording signals to the two input terminals of the recording head through the rotary transformer means;   wherein the differential input and the differential output of the reproducing amplifier means and the differential output of the recording amplifier means substantially eliminate crosstalk between the recording operation and the reproducing operation.